This invention relates to a hydraulic power trim and tilt apparatus for outboard motors and the like.
Outboard motors and the like are pendently mounted to the transom of a boat with a horizontal axis for selective tilt positioning of the lower unit of the outboard motor. The motor is normally tilted upwardly for transport and is trimmed relative to the boat for optimum propulsion. The motor is tilted from the running position for clearance during maintenance and trailering. The speed, and safety of propulsion, are effected by the degree of tilt or trim of the lower unit with respect to the boat and the angle at which the propeller generates its thrust forces.
With the development of high powered outboard motor units and the like various energy absorption systems have also been incorporated in the mounting of the outboard motors to prevent damage to the motor components and to occupants of the boat under power. Thus, if the lower unit strikes an object in the water with the boat moving at any significant speed, the lower unit is mounted to pivot upwardly over the object in order to prevent damaging of the boat and/or motor. Shock absorbing means are provided to prevent the engine from being kicked or thrown into the boat at the time of impace and similarly to absorb the forces during return movement of the motor.
Highly satisfactory combined tilt positioning and shock absorbing piston-cylinder units are disclosed in U.S. Pat. No. 3,434,448 to William Woodfill and U.S. Pat. No. 3,434,450 to Daniel McCormick. As more fully disclosed therein each of the piston cylinder units is provided with a piston having internal valves to permit the combined power actuating trim and tilt positioning while maintaining the shock absorbing characteristics of the assembly.
With the continuously increasing power and general increase in size of outboard motors, the tilt mechanisms are increased in power handling capabilities. The relatively high pressures are required to position and hold the devices in position. Consequently, the hydraulic piping and connections becomes an importance to prevent damage under normal operating conditions. Thus, the damping characteristic of the combined actuating and shock absorbing units may change with flexure of the hose and the like. The size also increases and increases the bulk of the outboard motor appearance. With the increase in weight associated with the larger outboard motors and the like, the angular orientation of the unit to properly tilt the mechanism and absorb the pivoting forces under normal operation require particular considerations to adequately operate over long periods of time.
In addition, the mounting apparatus normally includes mechanical lock mechanisms to lock the outboard motor unit in the raised position for trailing, maintenance and the like. In addition, a mechanical trim limit stop is desirably provided to establish a minimum trim position. A reverse lock is also normally provided to prevent the kicking up of the lower unit out of the water a result of the reverse propulsion forces.